Skyshine vs Direct Dose in MCNP5

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Discussion Overview

The discussion revolves around the definition and calculation of skyshine dose in the MCNP5 radiation transport code, particularly in scenarios involving shielding and distance from the radiation source. Participants explore the implications of different geometries and configurations on the skyshine component of radiation dose.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant seeks an accepted definition of skyshine dose in MCNP and questions how to calculate it when a large source region is involved.
  • Another participant suggests using an importance setting (imp:p 0) in the primary barrier to improve computational efficiency.
  • A participant shares their experience of using a high fictitious density slab in their initial tests but found that using imp=0 yielded faster and nearly identical results.
  • There is a question posed about the meaning of skyshine when there is no shield other than air and the source is relatively close to the dose point.
  • A definition of skyshine is provided, describing it as radiation scattered by air outside of radiological shielding.

Areas of Agreement / Disagreement

Participants express differing views on the best approach to model skyshine and its calculation, indicating that multiple competing perspectives remain unresolved.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about shielding and the specific configurations of source and dose points, which may affect the interpretation of skyshine.

Will_007
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TL;DR
how to calculate skyshine dose with mcnp?
Hello - what is an accepted definition of the skyshinne dose in MCNP and how would you calculate this? If you have a source and a shield a few meters away between the dose point, the contribution that goes around the shield would be skyshine....but..what if you have a big source region (e.g., a building) and your dose point is a mile away - how would you separate skyshine component?

Thanks
 
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Hi, you can consider an importance (imp:p 0) 0, in the primary barrier
 
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PSRB191921 said:
Hi, you can consider an importance (imp:p 0) 0, in the primary barrier
Hey - yeah. This was my ultimate choice. Initially I put in a slab with really high fictitious density in the middle of my shield (to allow stuff to scatter back and around to the dose location), but ran a test case and imp=0 was way faster and almost identical results.

if there is no shield (other than air), and source is 50 yards away from the dose point, what does skyshine mean to you?
 
"Skyshine" is a radiation scattered by sky air, outside the radiological
shielding.
In the first figure (geometry definition) in the second results with MCNP (reference Radiation Problems : From Analytical to Monte-Carlo Solutions ) :
skyshine.jpg
skyshineMCNP.jpg
 
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thanks
 

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